To access hidden easter egg track 21 on disc 1, play track 6 3 times to form 666.
To access hidden easter egg track 20 on disc 2, play track 6 2 times and then track 4 to form 664, however playing track 6 3 times will also give access to hidden video, but with more funny passage.

Recording information:

Disc 1 track 2 recorded live on December 21st, 1980 in London, United Kingdom.
Disc 1 track 10 recorded live on October 15th, 1986 in Sheffield, United Kingdom.
Disc 1 track 12 recorded live on June 12th, 1988 in Inglewood, California, United States.
Disc 1 track 13 recorded live on August 20th, 1988 in Castle Donington, United Kingdom.
Disc 1 track 14 recorded live on November 27th, 1988 in Birmingham, United Kingdom.
Disc 1 track 16 recorded live in September, 1990.

Disc 2 tracks 5, 6 recorded live on August 22nd, 1992 in Castle Donington, United Kingdom.
Disc 2 track 8 recorded live on November 1st, 1995 in Gothenburg, Sweden.
Disc 2 track 9 recorded live in November, 1995.
Disc 2 track 12 recorded live in May, 1995.
Disc 2 track 15 recorded live on January 19th, 2001 in Rio De Janeiro, Brazil.